feign 如何获取请求真实目的ip地址

FeignInvocationHandler
HystrixInvocationHandler

feign.SynchronousMethodHandler#executeAndDecode

Object executeAndDecode(RequestTemplate template) throws Throwable {
    Request request = targetRequest(template);
	.......
    Response response;
    long start = System.nanoTime();
    try {
      // 真正执行请求 
      response = client.execute(request, options);
      
      response.toBuilder().request(request).build();
    } catch (IOException e) {
      ....
      throw errorExecuting(request, e);
    }
    .....
  }

LoadBalancerFeignClient
org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient#execute

public Response execute(Request request, Request.Options options) throws IOException {
		try {
			URI asUri = URI.create(request.url());
			String clientName = asUri.getHost();
			URI uriWithoutHost = cleanUrl(request.url(), clientName);
			
			// 封装 ribbon 请求组件
			FeignLoadBalancer.RibbonRequest ribbonRequest = new FeignLoadBalancer.RibbonRequest(
					this.delegate, request, uriWithoutHost);
			IClientConfig requestConfig = getClientConfig(options, clientName);
			// 这行是关键
			return 
					// 获取 FeignLoadBalancer
					lbClient(clientName)
					// 负载之后请求真实的url
					// com.netflix.client.AbstractLoadBalancerAwareClient#executeWithLoadBalancer(....)
					.executeWithLoadBalancer(ribbonRequest,requestConfig)
					.toResponse();
		}
		catch (ClientException e) {
			....
			throw new RuntimeException(e);
		}
	}

com.netflix.client.AbstractLoadBalancerAwareClient#executeWithLoadBalancer(....)

public T executeWithLoadBalancer(final S request, final IClientConfig requestConfig) throws ClientException {
        LoadBalancerCommand<T> command = buildLoadBalancerCommand(request, requestConfig);
        try {
        	// 在com.netflix.loadbalancer.reactive.LoadBalancerCommand#submit 中会根据 负载均衡算法之后获取到真实的ip地址
            return command.submit(
                new ServerOperation<T>() {
                    @Override
                    // 传入的server 就是真实的ip
                    public Observable<T> call(Server server) {
                        URI finalUri = reconstructURIWithServer(server, request.getUri());
                        // 路径替换把原本 http://client-name/xxxx 地址改为 http://127.0.0.1:9090/xxxx
                        S requestForServer = (S) request.replaceUri(finalUri);
                        try {
                        	// 请求父类中的 execute 方法，也就是 上面 lbClient(clientName) 返回的 FeignLoadBalancer
                            return Observable.just(AbstractLoadBalancerAwareClient.this.execute(requestForServer, requestConfig));
                        } 
                        catch (Exception e) {
                            return Observable.error(e);
                        }
                    }
                })
                .toBlocking()
                .single();
        } catch (Exception e) {
            Throwable t = e.getCause();
            if (t instanceof ClientException) {
                throw (ClientException) t;
            } else {
                throw new ClientException(e);
            }
        }        
    }

org.springframework.cloud.openfeign.ribbon.FeignLoadBalancer#execute

@Override
 public RibbonResponse execute(RibbonRequest request, IClientConfig configOverride)
   throws IOException {
  Request.Options options;
  .....
  // 这里的 request 就是 `org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient#execute` 
  // 封装的FeignLoadBalancer.RibbonRequest
  // request.client() 返回就是 feign.Client.Default  
  Response response = request.client().execute(request.toRequest(), options);
  return new RibbonResponse(request.getUri(), response);
 }

feign.Client.Default#execute

 @Override
    public Response execute(Request request, Options options) throws IOException {
      HttpURLConnection connection = convertAndSend(request, options);
      return convertResponse(connection).toBuilder().request(request).build();
    }

org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient和feign.Client.Default

@Configuration
class DefaultFeignLoadBalancedConfiguration {
	@Bean
	@ConditionalOnMissingBean
	public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory,
				SpringClientFactory clientFactory) {
		return new LoadBalancerFeignClient(new Client.Default(null, null),
				cachingFactory, clientFactory);
	}
}

@Slf4j
public class InFeignClient extends Client.Default {
    /**
     */
    public InFeignClient(SSLSocketFactory sslContextFactory, HostnameVerifier hostnameVerifier) {
        super(sslContextFactory, hostnameVerifier);
    }
    @Override
    public Response execute(Request request, Request.Options options) throws IOException {
        try {
            return super.execute(request, options);
        } catch (IOException e) {
            log.warn(" 请求 {} 异常 ======> {}", request.url(), e.getMessage());
            throw e;
        }
    }
}

@Component
public class RestConfig {
    public CachingSpringLoadBalancerFactory cachingLBClientFactory(
            SpringClientFactory factory) {
        return new CachingSpringLoadBalancerFactory(factory);
    }
    @Bean
    public Client feignClient(SpringClientFactory clientFactory) {
        CachingSpringLoadBalancerFactory bean = cachingLBClientFactory(clientFactory);
        return new LoadBalancerFeignClient(new InFeignClient(null, null), bean, clientFactory);
    }    
}